[Bug c++/78567] New: GCC trunk fails to compile all-stage2-gcc in i386.c

["marc.mutz at kdab dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78567

            Bug ID: 78567
           Summary: GCC trunk fails to compile all-stage2-gcc in i386.c
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marc.mutz at kdab dot com
  Target Milestone: ---

Last successful built was 5th of October (yielding gcc version 7.0.0 20161005
(experimental) (GCC)), this failure persists since somewhen around the
beginning of November:

  make[3]: Entering directory '/home/marc/C++/gcc-build/gcc'
  /home/marc/C++/gcc-build/./prev-gcc/xg++
-B/home/marc/C++/gcc-build/./prev-gcc/ -B/d/gcc/trunk/x86_64-pc-linux-gnu/bin/
-nostdinc++
-B/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-B/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs

-I/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu
 -I/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/include 
-I/home/marc/C++/gcc/libstdc++-v3/libsupc++
-L/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs
-L/home/marc/C++/gcc-build/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs
-fno-PIE -c   -g -O2 -gtoggle -DIN_GCC     -fno-exceptions -fno-rtti
-fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror  
-DHAVE_CONFIG_H -I. -I. -I../../gcc/gcc -I../../gcc/gcc/.
-I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include 
-I../../gcc/gcc/../libdecnumber -I../../gcc/gcc/../libdecnumber/bid
-I../libdecnumber -I../../gcc/gcc/../libbacktrace   -o i386.o -MT i386.o -MMD
-MP -MF ./.deps/i386.TPo ../../gcc/gcc/config/i386/i386.c
  ../../gcc/gcc/config/i386/i386.c: In function ‘rtx_def*
ix86_expand_builtin(tree, rtx, rtx, machine_mode, int)’:
  ../../gcc/gcc/config/i386/i386.c:38407:18: error: ‘fcn’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
          emit_insn (fcn (target, accum, wide_reg, mem));
          ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1plus: all warnings being treated as errors
  Makefile:2198: recipe for target 'i386.o' failed
  make[3]: *** [i386.o] Error 1
  make[3]: Leaving directory '/home/marc/C++/gcc-build/gcc'
  Makefile:4589: recipe for target 'all-stage2-gcc' failed
  make[2]: *** [all-stage2-gcc] Error 2
  make[2]: Leaving directory '/home/marc/C++/gcc-build'
  Makefile:24513: recipe for target 'stage2-bubble' failed
  make[1]: *** [stage2-bubble] Error 2
  make[1]: Leaving directory '/home/marc/C++/gcc-build'
  Makefile:935: recipe for target 'all' failed
  make: *** [all] Error 2

Host compiler is

  $ g++ -v
  Using built-in specs.
  COLLECT_GCC=g++
  COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
  Target: x86_64-linux-gnu
  Configured with: ../src/configure -v --with-pkgversion='Ubuntu
5.4.0-6ubuntu1~16.04.4' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
  Thread model: posix
  gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 

Configure line:

  configure --prefix=/d/gcc/trunk --enable-checking=release
--enable-languges=c,c++,fortran,lto,objc,obj-c++

(out-of-souce build, clean except for config.status, which was how this build
was configured)